The new program, backed by the U.K.'s Department of Health and London Mayor Boris Johnson, was developed by StepJockey and includes an app and website that calculates how many calories are burned by taking the stairs.

Over the course of a day, people can scan "smart signs" posted at each staircase to keep track of how many calories they're burning. If a staircase hasn't been labeled yet, StepJockey gives climbers the opportunity to "rate" the stairway by providing enough information that the website can calculate how many calories would be burned by climbing it. The details can be printed on a poster and mounted on a wall.

"Anything that gets people more active and helps tackle obesity is a good thing in my book," said Johnson in a statement. "This initiative is a great mix of old-fashioned common sense and smart technology."

Even before the official launch on Thursday, at least 200 buildings in the U.K. have already had their stairways rated through the StepJockey website, and the county of Hertfordshire has already put up the "smart" posters in many of its municipal buildings.

But the effectiveness of calorie labels has recently come into question. In the United States, food labels listing calories have proliferated in restaurants and fast-food chains, but studies find calorie counts don't necessarily lead to healthier meal orders.

Polly de Mille, a registered clinical exercise physiologist and supervisor at Sports Performance at the Hospital of Special Surgery in New York, said there's a chance the signs could discourage people when they see how few calories they burn by climbing a few flights of stairs.

"One flight of stairs, it's not a lot of calories. You wonder if someone is seeing that and thinking, 'why bother? It's not even a stick of celery,'" said de Mille.

Instead of simply listing the numbers for calorie counts, de Mille said the StepJockey posters might be more persuasive if they described the other health benefits of taking stairs, such as how stairs can contribute to muscle strength.

"There are things that might appeal to people beyond the measly number of calories," said de Mille. "I try to take [the stairs] whenever I can, but it's more knowing it's good for my legs and gets my blood circulating. It makes me better at what I do."